Frame sealant is a key material during cell assembly process of liquid crystal panels. Frame sealant applied onto different sites will produce different effects. As shown in FIG. 1, the reference sign 1 represents edges of the whole glass substrate; 2 represents a substrate peripheral frame sealant (i.e., a frame sealant applied at the periphery of the whole substrate); 2′ represents a sub-substrate peripheral frame sealant (i.e., frame sealants applied at the peripheries of a plurality of small substrates attached to the same substrate) for preventing the edges of substrates and sub-substrates from bending deformation due to the self-weight of glass; 3 represents a primary frame sealant (i.e., a frame sealant applied at the periphery of the liquid crystal) serving as sealing the liquid crystal panels, reducing the contamination of the liquid crystal within the cell caused by external environment, and bonding the color film substrate and the array substrate.
During the cell assembly process, a color substrate (or an array substrate) having a frame sealant applied thereon, together with an array substrate (or a color film substrate) having liquid crystal applied thereon is first subject to cell assembling under vacuum, and then the frame sealant undergoes photo-curing and thermal curing with UV radiation and heating, thereby completing the cell assembling process. Moreover, during the cell assembling under vacuum, it should be ensured that there is only liquid crystal, without any residual gas, present in the sealing space formed by the primary frame sealant. As neither the substrate frame sealant nor the sub-substrate frame sealant has an opening, each of the space between the substrate peripheral frame sealant 2 and the sub-substrate peripheral frame sealant 2′ and the space between the sub-substrate peripheral frame sealant 2′ and the primary sealant 3 are under vacuum. Before the UV radiation and heating, the frame sealant is not yet cured, and the liquid crystal at the inner side of the primary frame sealant applies a certain pressure to the sealant, thereby resulting in that the pressure at the inner side the primary frame sealant is greater than that at the outer side of the primary frame sealant. The pressure difference between both sides will causes many problems, such as, impact of liquid crystal on un-cured frame sealant (briefly referred to as “liquid crystal puncture”), deformation (or even breakdown) of frame sealant, decreasing of the bonding force of frame sealant, and contamination of frame sealant to liquid crystal.
For solving the aforesaid problems caused by the pressure difference between the inner and outer sides of the primary frame sealant, it is conventional means to design openings in the substrate peripheral frame sealant and the sub-substrate peripheral frame sealant, through which external gases enter into all the regions except the inside of the primary frame sealant, so that the pressures inside and outside the primary frame sealant tends to equilibrium, thereby avoiding or alleviating the aforesaid problems of liquid crystal puncture.
However, for preventing the etching solution from entering into the sub-substrates to corrode the substrate during subsequent reduction process, the openings in the substrate peripheral frame sealant and the sub-substrate peripheral frame sealant need to be re-sealed, thereby complicating the process and increasing the cost.